.223 and benchmark - large extreme spreads?

The Hackmaster

The Hackmaster

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So I have never used benchmark in .223 before, but I have had good luck with ADI powders before so I decided to give it a try. Some loads showed promise accuracy wise, but all had very large extreme spreads. When I say large I mean as much as 120 FPS and generally not less than 70.

Is this normal for this powder? A google search didn't come up with anything.

Now, I'm not new to reloading. The first thing I did was try to see if somthing was malfunctioning. So I tested out a few things:

The Labradar was tested against hornady superformance factory ammo. ES was 40 FPS on 10 rounds. This is normal from what I have seen from other people testing the same ammunition on the labradar.

My handloads were tested in several different rifles. One 1-12 twist, and two 1-8. All showed large extreme spreads, but average velocity was about where the books say they should be for each given load.

I went home and tested the reloading scale with check weights. The scale appears to be fine.

Powder charges were book loads, starting at "start" loads and ending half a grain before max. All weighed and trickled up. It might be worth noting that all the top loads showed flattened primers.

Brass was Winchester, but after full length resizing I trim to length, uniform primer pocket, deburr flash hole and chamfer/deburr neck. Neck tension is .003. Shoulder bump is .006. All brass is within 1 grain+/-, which is fine for my needs. I'm not competing.

Bullets tested were the Nosler 50 grain ballistic tip varmint, the sierra 50 grain spitzer blitz and 50 grain varmint grenades. All loaded to manual specified lengths, as these are varmint rounds and I need them to feed from a magazine.

Primers were CCI BR-4, less than 3 years old from a sealed plastic box stored indoors. Powder was purchased last week from a store, not the trunk of someones car.


What the heck have I missed?!! I must have done something seriously wrong but I cant figure out where.
 
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I would chalk it up to your 0.006 shoulder bump. If the case is sized down too much, it will have more room to move around in the chamber. This allows for the case to move forward and rob energy from the firing pin as the primer is being struck, leading to large variations in velocity. Try going for the usual 0.002 of shoulder bump once the case is fully formed.
 
I`ve always found Benchmark to produce fantastic groups with 50 & 55 gr. bullets in a .223. Five shot 1/4" groups and sometimes less in a good gun. Nosler data says it was the most accurate powder tested with their 50 and 25.5 grains was the most accurate load tested, plus it gave the highest velocities of all powders tested. Anyway it works for me. I fire form the brass, trim, uniform flash holes & primer pockets, anneal, neck size with LEE collet die, seat .010 off and blast away.
 
goober23 said:
I would chalk it up to your 0.006 shoulder bump. If the case is sized down too much, it will have more room to move around in the chamber.
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I suspect this may be playing a large part. The .006 isn't somthing I was doing on purpose, I discovered that was what my redding sizing die did when I set it up normally. I might have to put some shim stock between the shell holder and the die before I tighten down the lock ring.
 
some data from Benchmark I've measured

204 Ruger, 4 shots : ES 41, SD 15
204 Ruger, 4 shots : ES 24, SD 10
223 Rem, 10 shots : ES 44, SD 13
223 Rem, 5 shots : ES 52, SD 18
223 Rem, 5 shots : ES 53, SD 18
223 Rem, 5 shots : ES 31, SD 14
6.5 Grendel, 14 shots : ES 89 SD 22
6.5 Grendel, 5 shots : ES 20 SD 9
223 Ackley, 4 shots : ES 28 SD 13
223 Ackley, 5 shots : ES 55 SD 20

Factory 53 Vmax ammo I've shot :
5 shots, ES 54, SD 21
5 shots, ES 50, SD 22
5 shots, ES 58, SD 22
20 shots, ES 145, SD 40


I put more weight into Standard Deviation numbers than I do extreme spread, which only factors in your two worst shots for variation. SD factors in every round
 
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Will 1F brass chamber easily in your action? If yes, just neck size and load the powder charge with the best groups so far. Compare to a charge 0.1gr more and less. Compare the data and groups.

If the issue is oversizing the case, this stuff will show much better numbers. Then you just need to size the brass to the 1F headspace and enjoy

Jerry
 
Even with the 223 I've seen big improvements in SDs going to CCI 450 magnum primers from BR4s. Not always, but may be worth testing.
Other SD improvements I've seen were going from 0.003" neck tension to as low as 0.001" using mandrels instead of the sizing ball. Minimal shoulder bump/neck sizing would be the first thing I'd try.
 
Bad Bob said:
I`ve always found Benchmark to produce fantastic groups with 50 & 55 gr. bullets in a .223. Five shot 1/4" groups and sometimes less in a good gun. Nosler data says it was the most accurate powder tested with their 50 and 25.5 grains was the most accurate load tested, plus it gave the highest velocities of all powders tested. Anyway it works for me. I fire form the brass, trim, uniform flash holes & primer pockets, anneal, neck size with LEE collet die, seat .010 off and blast away.
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When I used Benchmark in my 24" bull barrel target AR it gave the best accuracy of any of the 5 or 6 powders I tested. 5 shots into .28" was my best but the other groups were not far behind. Just weighed the bullets (Sierra Match King 52 gr.), cases & powder, trimmed cases to length and loaded the ammo. I never measured SD or ES but with groups that size I really wouldn't care what they were anyway.
 
So, after another range trip I have more questions than answers. I applied the suggestions listed in this thread and I managed to get the extreme spreads down...but only with the 50 Grain nosler ballistic tips. The sierra 50 grain blitz and the 50 grain varmint grenades both showed extreme spreads as high as 175 FPS. I tested this in several rifles. The sierra 1340 ES suprises me as my .222 shoots the same bullet with the same powder and primer with an ES of less than 40.

The ballistic tips showed ES of 40 and sd of 20ish. Why only one bullet would co-operate I have no idea, but it's a working solution for now. For reference I tested the Hornady superformance 53 grain VMax through the labradar. They had an ES of 6 and a velocity of 3550 fps from a 26" barrel. The group was 2" at 100 yards though.



Ganderite said:
Did you do anything that would have made the flash hole bigger? ES is inversely proportionate to flash hole size.
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I dont think so. I use a sinclair flash hole uniforming tool to deburr and reshape the inside of the case slightly. The pilot that goes through the flash hole is slightly smaller than the hole itself.
 
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